The present invention relates to a control apparatus for a carbureter for controlling an idling engine speed, and more particularly to a control apparatus having a combination of a plurality of idle-up means capable of retaining an optimum idling engine speed under any load condition.
As a conventional technique for controlling the idling engine speed of an engine with a carbureter, there is disclosed a technique, e.g., in Japanese Utility Model Laid-open Application No. 55-137234. According to this technique, a negative pressure responding unit as an idle-up means is cooperatively coupled to a throttle valve, and the throttle valve is opened or closed by actuating an electromagnetic valve in response to a signal from a calculation unit upon activation of the negative pressure responding unit in accordance with the negative pressure or an atmospheric pressure.
According to the above-described conventional technique, only the negative pressure responding unit cooperatively coupled to the throttle valve is used as the idle-up means, so that only a single high idling engine speed is obtained. As a result, if two or more loads are applied or if the operating condition of one load changes relatively greater a proper idling engine speed is not possible to be retained.
In recent years, air conditioners are widely used for vehicles. An air conditioner is often used during an idling state of the engine. The load of the air conditioner is imposed directly upon the engine and is very large as compared with another electric load. The load of the air conditioner also changes greatly with the temperature of atmosphere. It is therefore necessary to control the idling engine speed and retain an idle-up control of the engine, in accordance with whether or not the air conditioner is used and in accordance with the load condition of the air conditioner, while considering other load conditions.